1.1 Introduction

1.1.1 Why is cleanroom necessary?
In the high technological industries such as electronics, optical and biological industries, the newly developed commodities are manufactured with precise fabrication as a basic process. Both production yield and product quality are, therefore, affected by invisible airborne particles or dust. For example in manufacturing of semiconductors, the design rule of ULSI is now minimized to the line width of submicron. In this case, the size of particle to be eliminated in the cleanroom is smaller than 0.05 μm, namely, 1/5 ~ 1/10 of the design rule, which means that only a super clean environment can be accepted for its production process.

Also, in food processing, medical or pharmaceuticals, how to control the micro-organism is a key point to maintain the quality, which can be performed by cleanroom.

1.1.2 What is a cleanroom?
Cleanroom is defined as “a specially constructed room in which the air supply, air distribution, dust and airborne particle, room pressure, temperature and humidity are environmentally regulated to meet appropriate cleanliness level”.

Particle referred here means a particle as small as 1/1000 of human hair in diameter, which is equivalent to 1/100 of the smallest visible limit. These small particles affect production yield and product quality to a great extent.

Air filters being used in common HVAC system can never collect these particles. Also many factors other than air supply are to be carefully managed to make clean environment condition.

Cleanroom is what solves these subjects.

Cleanroom is divided into two kinds by application; one is Industrial Cleanroom and the other iological Cleanroom. The latter, together with cleanroom function, controls contamination density of
micro-organism and plays an important role in clinical research and examination, development of edicines, research and improvement of cultivation cycle and plant breeding, etc.

Generally, a high efficient filter is used, and its development has now advanced from 0.3 μm HEPA Filter (High Efficiency Particulate Air Filter) to ULPA Filter (Ultra Low Penetration Air Filter) which can eliminate 0.1 – 0.2 μm particles in diameter at an efficiency of 99.999%.